Conventionally, in a postal mail classification system or a physical distribution system, a barcode reading system is used as a system to sort mail articles or delivered articles. A barcode reading system reads a barcode printed on a mail or delivered article and acquires address data or delivery destination data from a read-out ID. Mail or delivered articles are sorted into sorting boxes each corresponding to an address in a delivery service area based on the data. Recently, use of an image reader, which substitutes for such a barcode reading system, is increasing. An image reader is used for acquiring numerical data from an image obtained by scanning a surface of a mail or delivered article to identify the mail or delivered article.
FIG. 10 shows a block diagram of an example of an image comparing apparatus 900 of the related art. This image comparing apparatus 900 includes an image input unit 901, a feature extraction unit 902, a feature storing unit 903, a comparing unit 904 and a comparison result output unit 905. The image input unit 901 scans a character or the like on a sheet to convert it into image data processible by a computer. The feature extraction unit 902 converts the image data obtained by the image input unit 901 into a numerical data. The feature storing unit 903 stores the numerical data obtained by the feature extraction unit 902 with an index, corresponding to the character or the like on the sheet. The comparing unit 904 compares the numerical data extracted from the image with plural numerical data, which are extracted from plural images registered in advance in the feature storing unit 903. The comparison result output unit 905 outputs the index, which is a comparison result by the comparing unit 904.
Next, processing of the image comparing apparatus 900 of FIG. 10 will be described with reference to the flowchart of FIG. 11. First, the image input unit 901 scans a surface of a sheet. Image data of a character, a symbol, an image, or the like on the sheet is obtained (Step S901). Next, the feature extraction unit 902 extracts a feature of the image data inputted from the image input unit 901 (Step S902). Extraction of the feature, specifically, is a conversion from an image data to a numerical data using, for example, information obtained from texture information of image or an adjacency relationship for connected components of image.
Next, it is selected whether the numerical data obtained from the image data is newly registered in the image comparing apparatus 900, or the numerical data is compared with numerical data stored in advance in the feature storing unit 903, (Step S903). The image comparing apparatus 900 may be realized by a personal computer or a workstation. The above mentioned two options may be shown on a display attached to such an apparatus, and selected by operation of a keyboard or a mouse.
When the option of registration is selected in Step S903, an index (ID) is newly generated (Step S904). The index may be selected discretionary, unless the same index has been registered in advance in the feature storing unit 903. Next, the numerical data extracted in Step S902 and the index generated in Step S904 (ID) are registered in the feature storing unit 903 (Step S905), and the processing ends.
On the other hand, when the option of comparison is selected in Step S903, the comparing unit 904 compares the numerical data extracted in Step S902 with the numerical data registered in advance in the feature storing unit 903 and similar to the extracted numerical data (Step S906). Then, it is examined whether there is a numerical data determined to be identical to the extracted numerical data in the plural numerical data stored in the feature storing unit 903 (Step S907).
When there is a numerical data determined to be identical in Step S907, an index (ID) given to the numerical data determined to be identical is outputted from the comparison result output unit 905 (Step S908), and the processing ends. On the other hand, when there is no numerical data determined to be identical, the comparison result output unit 905 outputs a result that there are no objects to be identified (Step S909), and the processing ends.
Japanese Patent Application Laid-Open No. 2000-011088 discloses an image comparing apparatus, which recognizes a character, comprising: a scanner for optically reading a surface of an address side of a mail article and converts a scanned image into image data of the mail; and a feature extraction unit which extracts image information such as a destination address and a zip code from the image data of the mail. In this image comparing apparatus, the feature extraction unit extracts four kinds of image feature information every 512 pixels included in one scanning line, and stores the information into a feature memory. Image feature information is a histogram showing a density frequency distribution of image, low-resolution multi value data, medium-resolution binary data and high-resolution binary data. As a result, a frame memory, which temporarily saves pixel gray data of the whole screen to be read, pixel gray data after a character region is clipped and pixel gray data after a line is clipped, becomes unnecessary.
Republication of PCT international application WO2002/029720 discloses an image comparing apparatus, which compares fingerprint images. A similarity between a part of feature information extracted from a fingerprint image of a registrant and a part corresponding to the registered fingerprint is calculated. A fingerprint image determined to be identical is narrowed down without extracting supplementary information. As a result, fingerprint comparing time is reduced. Identity is determined from the calculated similarity, and the registered fingerprints are narrowed down. By determining similarity between a fingerprint image of an person to be identified and the registered fingerprint which has been narrowed down according to the feature information, a fingerprint image to be performed identity determination is narrowed down.